SOFC Oxy-Combustion Cycle for High-Efficiency CO2 Capture
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Solution Overview
Problem
Current energy conversion systems face inefficiencies in converting gaseous and liquid fuels into electricity while capturing CO2 effectively, with limitations in net electric efficiency and material costs due to severe operating conditions.
Innovation Solution
Integration of a Solid Oxide Fuel Cell (SOFC) unit with a semi-closed oxy-combustion cycle using CO2 as the main working fluid, allowing for high-pressure operation and efficient energy conversion with unconverted fuel and oxidant streams, and utilizing unconverted oxygen in the combustor, forming a Solid Oxide Semi-closed CO2 cycle (SOSCO2).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high turbine inlet temperatures (1100-1300°C) are used to achieve high efficiency, then net electric efficiency improves, but material costs increase due to requirement of directionally-solidified superalloys and blade cooling
Solution Approach 1:
The patent changes the operating temperature parameter from conventional high temperatures (1100-1300°C) to moderate temperatures (650-750°C at regenerator inlet), allowing the use of conventional alloys instead of expensive directionally-solidified superalloys while maintaining high efficiency through the integrated SOFC-GT hybrid cycle configuration
Solution Approach 2:
The patent replaces the conventional mechanical combustion-based gas turbine system with a hybrid system that incorporates electrochemical energy conversion through SOFCs, substituting part of the thermal-mechanical conversion process with direct electrochemical conversion to reduce temperature requirements
2Loss of energy
If regenerator inlet temperature is increased to 650-750°C to improve efficiency, then net electric efficiency improves, but material costs increase due to requirement of special alloys like Ni-based Inconel 617
Solution Approach 1:
The patent optimizes the regenerator inlet temperature parameter to a moderate range (650-750°C) that balances efficiency requirements with material cost constraints, enabling the use of conventional alloys rather than expensive Ni-based superalloys like Inconel 617
3Device complexity
If atmospheric pressure operation is used to simplify system design, then device complexity decreases, but CO2 capture efficiency deteriorates because the system cannot produce a concentrated CO2 stream
Solution Approach 1:
The patent performs preliminary oxygen separation through the SOFC cathode before combustion, creating a pre-concentrated oxygen stream that enables efficient CO2 capture in the exhaust, eliminating the need for complex post-combustion separation systems
Solution Approach 2:
The patent merges the oxygen separation function with the combustion process by using the SOFC cathode to concentrate oxygen that is then directly fed to the combustor, combining two separate functions (oxygen separation and combustion) into an integrated system
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves higher net electric efficiencies (up to 75%) with reduced material costs and operational flexibility, enabling zero pollutant and greenhouse gas emissions when CO2 is captured, and operates at less severe temperatures suitable for uncooled turbines and conventional alloys.
Implementation Method 1
A SOFC unit (100) having an anode and a cathode side, receiving a fuel (1) and a stream of oxidant (4) for converting a fraction of chemical power of fuel (1) directly into electric power through a plurality of electrochemical reactions
Implementation Method 2
a combustor unit (200), converting unconverted fuel (5) and unconverted oxidant (6) into a product gas (10)
Implementation Method 3
an expander unit (300) expanding the product gas (10) exiting the combustor (200) into a expanded gas (13)
Data Source
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AI summary
The present invention relates to an energy conversion system comprising: - a Solid Oxide Fuel Cell (SOFC) unit (A) having an anode and a cathode side, configured for receiving a fuel (1) and a steam of oxidant (4) and for converting a fraction of chemical power of the fuel (1) directly into electric power through one or more electrochemical reactions occurring on the anode and the cathode side of the SOFC unit (A) involving said fuel (1) and said oxidant (4), parts of the fuel (1) and of the steam of oxidant (4) being maintained unconverted following said electrochemical reactions; - a combustor unit (B) arranged to receive the unconverted fuel (5) and the unconverted oxidant (6) from the SOFC unit (A), configured for the combustion of the unconverted fuel (5) using the unconverted oxidant (6), thereby converting the unconverted fuel (5) and the unconverted oxidant (6) into product gas (10); - an expander unit (C) arranged to receive the product gas (10) exiting the combustor (B) and configured for expanding said product gas (10) exiting the combustor (B) into flue gas (12)being; - a cooler unit (E) in thermal relationship with a heat sink (27) and configured for cooling said flue gas (12) exiting the expander unit (C); - a separator (F) for removing condensed species (15) from the cooled gas (14) exiting the cooler unit (E), thereby obtaining a recycled stream (18); and - a first compression unit (K) configured for increasing the pressure of said oxidant (26, 4, 8) to a value suitable for the SOFC unit (A) and the combustor unit (B).